Yellow, Oily, Gas mixture in Intake Plenum - ???????

[prayers1 153]

I've taken my carb off and found on the ribbed plenum floor a yellow, oily, gas mixture.  In the past I was getting oil sucked into the intake via the PCV, so I took it off and just have breathers on both valve covers.  I was surprised to see this new discovery mixture lying within the intake.

 

I try to always run the highest octane gas with no ethanol. Every now and then if I'm long distance I fill up at a station that might have ethonal.

 

I had a engine builder friend come over and he said it was gas broken down by heat.

 

It's had to believe that, because it has an oily base to it.

 

There is a picture below showing what it looks like.

 

I was wondering if you all agree with him of have another thought.

Thanks!

[moodster 55]

Mine looks exactly the same.  The heavier molecules of gas are what collects on the intake passages.  The lighter more vaporous parts get burned completely.  As to the color, I couldn't tell you why it is yellow.

 

david

[MikeStang 247]

Ewww someone took a piss in your intake HaHa.

 

No sweat tho mine has that sometimes also.

May want to look at a carb overhaul tho...perhaps your carb is dribbling or boiling over the fuel and its pooling up right there.

[prayers1 153]

Never thought of the boiling concern, I had thought that that area of the intake would be super clean since the rush of air mixed with gas would always keep it clean.

 

I did notice that the last time I had the car out and pulled back into the garage, I noticed that the fuel line from th epump to carb was extremely hot.

 

Would a bottle of that tank additive fuel cleaner be of any benefit?

[ray1970 88]

Without getting into it to deep.

Intakes need to have a wet film to work properly.Think of gas crawling down the sides.

EX ports are a dry port..

 

This is one of the transitions that can make jetting a little bit of a challenge at times..

 

Intakes need to be wet...If you shut the car off it will puddle to the lowest point it can find.. 

 

The gas that is crawling is more like thin oil after the less solid stuff has moved on..

 

Understand??

[1969_Mach1 333]

It's fuel.  I've seen a film of fuel, but never puddles.  All in all it doesn't look too bad.  Like MikeStang mentioned, the carb might be dribbling or boiling over after you shut off the engine.  Might be something inherent to the intake manifold design.  I don't understand ray1970's analogy.

[prayers1 153]

It's a by product of fuel. I sprayed some carb cleaner in it and it cleaned it as new. If it was oil it would of left a film and a little harder to clean.

 

I never knew this happen, I was alarmed at first.

Thanks Guys for helping me resolve this!

[1969_Mach1 333]

By product of fuel?????  Another one I don't understand.  To me that doesn't explain the puddling.  If it is a byproduct of fuel, why would there be standing fuel long enough to leave a puddle of "by product" behind.  I need more information before believing that one.